205M Parr 1108 Oxygen Bomb Inst

NO. 205M

1108 Oxygen Combustion Bomb

Operating Instruction Manual

Parr Instrument Company

P a r r I n s t r u m e n t C o m p a n y2

1108 Oxygen Combustion Vessels

Scope

These instructions cover the procedures to be followed when using a Parr 1108 Oxygen Combustion Bomb to determine calorific values of solid or liquid combustible material in a Parr calorimeter, or when using an 1108 bomb in a 1901 Oxygen Bomb Apparatus to prepare solid or liquid samples for chemical analysis. The user should study these instructions carefully in order to obtain a complete understanding of the capabilities and limitations of an 1108 Bomb, and to be well aware of the precautions to be observed in its operation. Calorimeter operations and the operation of various oxygen bomb accessories are described in separate instruction manuals listed below, copies of which are available upon request.

Related InStRuctIonS

No. Description

201M Limited Warranty 207M Analytical Methods for Oxygen Bombs230M Safety in the Operation of Laboratory and Pres-

sure Vessels483M Introduction to Bomb Calorimetry

Scope — 2

Related InStRuctIonS — 2

opeRatIng the 1108 oxygen BomB — 3Precautions — 3Special Alloy Construction — 3A Chlorine-Resistant Bomb — 3Other Special Purpose Bombs — 3Allowable Sample Size — 3Attaching the Fuse — 3Liquids in the Bomb — 4Closing the Bomb — 4Filling the Bomb — 5Firing the Bomb — 5Recovering the Combustion Products — 6An Optional Recovery Procedure — 6

SampleS and Sample holdeRS — 7Particle Size and Moisture Content — 7Combustion Aids — 7Sample Pellets — 7Combustion Capsules — 7Foodstuffs and Cellulosic Materials — 8Coarse Samples — 8Corrosive Samples — 8Liquid Samples — 8Gelatin Capsules — 9Tape-Sealed Sample Holders — 9Heavy Oils — 9Explosives and High Energy Fuels — 10

opeRatIng SuggeStIonS — 10Poor Combustion — 10Oxygen Charging Pressure — 10

maIntenance and Safety InStRuctIonS — 10Bomb Maintenance — 10

1108 paRtS dIagRam Key — 12Bomb Repairs and Proof Tests — 12

paRtS foR the 1108 oxygen BomB — 13

paRtS foR the 2901 IgnItIon unIt — 14

paRtS foR the 1825 oxygen fIllIng connectIon — 15

table of contentS

w w w . p a r r i n s t . c o m 3


OPERATING THE 1108 OXYGEN BOMB

Precautions Combustion with oxygen in a sealed bomb is a very effective and reliable method for releasing all heat energy obtainable from a sample and for preparing hydrocarbon compounds and carbonaceous materials for analysis, but there are certain precautions which must always be observed when using this equipment. In particular:

Do not overcharge the bomb with too much sample • or with a sample which might react with explosive violence.Do not overcharge the bomb with too much oxygen. • The initial charging pressure should not exceed 40 atm (590 psig).Do not fire the bomb alone on an open bench • without providing a protective cooling medium. The bomb should be completely submerged in water during firing.Do not fire the bomb if gas bubbles are released • from any point on the bomb when it is submerged in water.Do not ignite a volatile sample without using one of • the sealed sample holders described on page 9 or the tape technique.Stand away from the bomb during and do not • handle the bomb for at least 6 minutes after firing.Keep the bomb in good condition at all times. Any • parts that show signs of weakness or deterioration must be replaced promptly.Read the maintenance and safety instructions • beginning on page 10 before starting to use the bomb, and urge all operating personnel to re-read these instructions often.Screw caps and cylinders are stamped so that • each cylinder and screw cap can be identified as a matched set. We recommend that you maintain the match of cylinders and screw caps for your safety and ease of use.

Special Alloy ConstructionThe standard 1108 oxygen bomb is made of a special columbium-stabilized stainless steel selected for it’s excellent resistance to the mixed nitric and sulfuric acids generated in a bomb combustion. It is a superior alloy which will withstand the conditions generated in almost all fuel testing applications, yet neither it nor any other stainless steel will resist the corrosive atmospheres produced when burning samples containing halogen compounds. For these applications, Parr offers the

1108CL bomb described below. It should be noted that all instructions for the 1108 bomb apply equally to the 1108CL bomb as well.

A Chlorine-Resistant BombThe 1108CL bomb is the same as the standard 1108 model, but with a head and cylinder made of an alloy with superior corrosion resistance to the free chlorine and halogen acids released when burning chlorinated samples. Users who analyze waste materials and combustible solvents are urged to select the 1108CL bomb instead of 1108 for its longer service life under extreme corrosive conditions. Bomb maintenance is also improved. In most cases, 1108CL bombs returned to the factory for scheduled maintenance can be restored to optimum finish by repolishing instead of having to rebore the cylinder to remove pits.

Other Special Purpose BombsAlthough the 1108 and 1108CL bombs will handle a broad range of test samples, Parr also offers other special purpose combustion bombs, including: a high pressure bomb for explosives, an oversize bomb for large samples and a semi-micro bomb for small samples. Separate operating instructions are issued for these special bombs.

Allowable Sample Size To stay within safe limits, the bomb should never be charged with a sample which will release more than 8000 calories when burned in oxygen, and the initial oxygen pressure should never exceed 40 atmospheres (590 psig). This generally limits the mass of the combustible charge (sample plus benzoic acid, gelatin, firing oil or any combustion aid) to not more than 1.1 grams. When starting tests with new or unfamiliar materials it is always best to use samples of less than 0.7 of a gram, with the possibility of increasing the amount if preliminary tests indicate no abnormal behavior. To avoid damage to the bomb and possible injury to the operator, it should be a standing rule in each laboratory that the bomb must never be charged with more than 1.5 grams of combustible material.

Attaching the FuseSet the bomb on an A38A support stand and fasten a 10 cm length of fuse wire between the two electrodes. Parr 45C10 nickel alloy wire is used for most tests, with platinum wire offered as an alternate for certain special procedures. The 45C10 wire is furnished on cards from which uniform 10 cm lengths can be cut without further measurement.



Quick-grip electrodes now installed in all new 1108 oxygen bombs eliminate most of the threading and twisting formerly required when binding the wire to plain electrodes. To attach the fuse to quick-grip electrodes, insert the ends of the wire into the eyelet at the end of each stem and push the cap downward to pinch the wire into place. No further threading or twisting is required. The procedure for binding the fuse to the 4A and 5A plain electrodes in older Parr bombs is illustrated in the instruction manual furnished with the original equipment. For convenience, it is recommended that the user purchase and install new 4A10 and 5A10 quick-grip electrodes as replacements for the 4A and 5A styles in older equipment.

Place the fuel capsule with its weighed sample in the electrode loop and bend the wire downward toward the surface of the charge as shown above. It is not necessary to submerge the wire in a powdered sample. In fact, better combustions will usually be obtained if the loop of the fuse is set slightly above the surface. When using pelleted samples, bend the wire so that the loop bears against the top of the pellet firmly enough to keep it from sliding against the side of the capsule. It is also good practice to tilt the capsule slightly to one side so that the flame emerging from it will not impinge directly on the tip of the straight electrode.

Liquids in the BombMost bomb combustion procedures call for a small amount of liquid to be placed in the bottom of the bomb as a sequestering agent and absorbent. If the amount and type of liquid are not otherwise specified, add 1.0 mL of distilled or deionized water from a pipet.

Closing the BombCare must be taken not to disturb the sample when moving the bomb head from the support stand to the bomb cylinder. Check the sealing ring to be sure that it is in good condition and moisten it with a bit of water so that it will slide freely into the cylinder; then slide the head into the cylinder and push it down as far as it will go. For easy insertion, push the head straight down without twisting and leave the gas release valve open during this operation. When working with older bombs which have a removable compression ring, be sure that the 104A2 ring is in place above the gasket before attaching the screw cap. Current model A416A3 bomb heads do not require a separate compression ring. Set the screw cap on the cylinder and turn it down firmly by hand to a solid stop. When properly closed, no threads on the cylinder should be exposed. If the screw cap tends to bind to the cylinder at this point, indicating that it might be difficult to open the bomb after it has been fired, turn the screw cap back slightly – but only a few degrees – enough to release the binding, since the bottom thread must remain fully engaged. It is not necessary to use a wrench or spanner on the screw cap. Hand tightening should be sufficient to secure a tight seal.

45C10 Fuse Wire

Set the bomb head on the A38A support stand when attaching the fuse and arranging the sample.

To attach the fuse: raise the cap, insert the wire through the eyelet, then pull the cap downward to completer the assembly.A38A Bomb Head Support Stand



1825 Oxygen Filling Connection

Filling the BombThe instructions below describe a manual system using the 1825 Oxygen Filling Connection furnished with other Parr apparatus.

Oxygen for the bomb can be drawn from a standard commercial oxygen tank. Unscrew the protective cap from the tank and inspect the threads on the valve outlet to be sure they are clean and in good condition. Place the ball end of the connection into the outlet socket and draw up the union nut tightly with a wrench, keeping the 0-55 atm gage in an upright position.

The pressure connection to the bomb is made with a slip connector on the oxygen hose which slides over the gas inlet fitting on the bomb head. Slide the connector onto the inlet valve body and push it down as far as it will go. If it does not slide easily, a drop of water spread around the inlet valve will lubricate the sealing rings. Older bombs use a threaded connector with a knurled coupling which must be turned finger tight.

Close the outlet valve on the bomb head; then open or “crack” the oxygen tank valve not more than one-quarter turn. Open the filling connection control valve slowly and watch the gage as the bomb pressure rises to the desired filling pressure (usually 30 atm., but never more than 40 atm.); then close the control valve. The bomb inlet check valve will close automatically when the oxygen supply is shut off, leaving the bomb

filled to the highest pressure indicated on the 0-55 atm. Gage. Release the residual pressure in the filling hose by pushing downward on the lever attached to the relief valve. The gage should now return to zero. If the pressure drops slowly and a large amount of gas escapes when the pressure relief valve is opened, the check valve in the bomb head is not operating properly. This trouble will have to be corrected before the bomb can be used. If too much oxygen should accidentally be introduced into the bomb, DO NOT proceed with the combustion. Detach the filling connection; exhaust the bomb; remove the head and reweigh the sample before repeating the filling operation.

2901 Ignition Unit Firing the Bomb The electric current for firing the bomb should be drawn from a Parr 2901EB Ignition Unit connected to an 115v50/60Hz grounded electrical outlet. (For 230v50/60Hz use a 2901EE Ignition Unit). Connect one of the lead wires from the calorimeter to the 10 cm binding post on the ignition unit and the 2nd wire to the middle or “common” terminal.

When using the bomb in a calorimeter, insert the 421A lifting handle into the two holes in the side of the screw cap and lower the bomb partially into the calorimeter water bucket. Press the banana plugs on the two ignition wires firmly into the terminal sockets on the bomb head before the head is completely immersed in the water. After connecting the wires, lower the bomb into the bucket with its feet spanning the circular boss in the bottom of the bucket. Remove the lifting handle and shake off any drops of water back into the bucket. Be careful not to remove any water from the bucket with the fingers.



When using the bomb alone for analytical purposes it should be connected to the ignition unit as described above and held submerged in an A387A or similar water bath during firing.

In all operations, check the bomb for leaks before firing. If any gas leakage is indicated, no matter how slight, DO NOT FIRE THE BOMB. Instead remove it from the water bath; release the pressure and eliminate the leak before proceeding with combustion test. If no leakage is indicated, adjust the water flow rate so that the bomb will be covered by a continuous flow of cold water during the firing period, then stand back and press the firing button on the ignition unit to fire the charge.

Caution: Do not have the head, hands or any parts of the body directly over the bomb during the firing period and do not go near the bomb for at least 20 seconds after the firing.

Fire the charge by pressing the firing button on the ignition unit, keeping the circuit closed for about 5 seconds. The indicator light will come on when the button is depressed and will remain on while current flows through the fuse. When the fuse burns off and breaks the circuit, the light will go out. Normally this takes about ½ second, but it is good practice to keep the push switch closed for about 5 seconds regardless of the light. If the light continues to glow while the button is depressed, there is either a short circuit in the firing system or the fuse was not properly arranged. If a 26 gauge platinum wire is used to fire the charge, hold the firing button down for only one or two seconds which should be sufficient to ignite the auxiliary fuse. A longer period may melt the wire. If the wire melts, use the 7 cm terminals on the ignition unit to obtain a lower firing voltage; or add a heavy, one-ohm resistor to the 10 cm firing circuit to lower the voltage.

If the indicator light does not come on when the firing button is pressed there is either a fault in the 2901 or an open circuit in the system. Check for voltage between the 10 cm and common terminals of the 2901. Approximately 23 VAC should be measured. If there is no voltage present, check the fuse inside the 2901. An open circuit can usually be located with an ohmmeter. Flex the lead wires during any continuity check as the wires may be broken and making only intermittent contact. If the red indicator light glows during ignition but the bomb fuse does not burn, check the system for a voltage leak to ground, most likely in the insulated electrode on the bomb head. Check the electrode using

the high impedance scale on an ohmmeter and replace the electrode insulator and seal if leakage is indicated.

Recovering the Combustion ProductsLet the bomb stand in the calorimeter or water bath for at least 3 minutes, then lift it out of the water and wipe with a clean towel. Open the valve knob slightly to release all residual gas pressure before attempting to remove the screw cap. Gas release should proceed slowly over a period of not less than one minute to avoid entrainment losses. After all pressure has been released, unscrew the cap; lift the head out of the cylinder and place it on the support stand. Do not twist the head during removal. Pull it straight out to avoid sticking. Examine the interior of the bomb for soot or other evidence of incomplete combustion. If such is found the test will have to be discarded. Wash all interior surfaces of the bomb and the combustion capsule with a jet of distilled water and collect the washings. If any precipitate or residue is present, remove it with a rubber policeman. Do not filter the washings as this might remove valuable constituents. Titrate the washings and measure the unburned fuse wire as required for calorific tests, then analyze the washings for sulfur and other elements, if required.

An Optional Recovery ProcedureIf desired, a luer fitting, 518A, can be attached to the bomb to provide a means for washing the bomb and recovering the combustion products with a syringe without opening the bomb and removing the bomb head. To use this procedure, remove the standard A420A valve needle and replace it with an A420A2 needle to which a syringe, 244C, can be attached.

To recover the combustion products via a luer fitting, let the bomb stand in a cooling bath for at least 3 minutes after firing to allow for complete condensation of all residual vapor. Then remove the bomb from the water and attach only the barrel of a 244C syringe to the luer fitting. Open the valve and release the pressure at a slow rate, using at least a full minute to bring the bomb pressure back to atmospheric. The attached syringe barrel will help to retain any condensate spray that might be carried out of the valve during the exhaust period.

Add 30 mL of distilled water to the attached syringe barrel and use the syringe plunge to force the water into the bomb, then close the valve while holding the plunger down. This will develop sufficient pressure within the bomb to seat the inlet check valve and provide enough



positive pressure to help remove the washings. Agitate and rotate the bomb in a horizontal position to wet all inner surfaces, then turn the bomb upside down over a 600 mL beaker and open the valve to discharge the washings into the beaker. Tilt the bomb slightly toward the valve to get as much of the water out as possible. Repeat this back-flushing procedure two times, collecting a total of 90 to 100 mL of washings, then open the bomb and recover any liquid that may remain in the cylinder. The three complete back flush and rinse cycles should recover better than 99 percent of the combustion products.

SAMPLES AND SAMPLE HOLDERS

Particle Size and Moisture Content Solid samples burn best in an oxygen bomb when reduced to 60-mesh, or smaller, and compressed into a pellet with a Parr Pellet Press. Particle size is important because it influences the reaction rate. Large particles may not burn completely and small particles are easily swept out of the capsule by turbulent gases during the rapid combustion. Compression into a pellet is recommended since a pellet burns less vigorously than a loose sample, resulting in fewer incomplete combustions.

Materials such as coal burn well in the as-received or air-dry condition, but do not burn bone-dry samples. A certain amount of moisture is desirable in order to control the burning rate. Very dry samples may burn so rapidly that a flame might reach the seals or the soft valve seat in the bomb head, igniting these parts and possibly causing a serious burn-out through the head. Moisture contents up to 20% can be tolerated in many cases, but the optimum moisture is best determined by trial combustions. If moisture is to be added, drop water directly into a loose sample or onto a pellet after the sample has been weighed; then let the sample stand for awhile to obtain uniform distribution.

Combustion AidsSome samples may be difficult to ignite, or they may burn so slowly that the particles become chilled below the ignition point before complete combustion is obtained. In such cases benzoic acid, white oil or any other combustible material of known purity can be mixed with the sample. Ethylene glycol, butyl alcohol or decalin may also be used for this purpose. It must be remembered, however, that a combustion aid adds to the total energy released in the bomb and the amount of

sample may have to be reduced to compensate for the added charge. If benzoic acid is added as a combustion aid, it must be added in a pellet form, .2 gm pellets. Never combust benzoic acid in powder form.

2811 Pellet Press

Sample PelletsOne of the most useful techniques for handling powdered samples is to compress the material into a tablet or pellet before it is weighed. Pellets are easier to handle than loose samples and they burn slower in the bomb, thereby reducing the chances for incomplete combustion. The Parr pellet press offers a convenient means for preparing samples in this manner. Pellets produced in this press are ejected into a stainless steel receiver from which they can be lifted and handled easily with a pair of forceps. Most pellets for use in the 1108 oxygen bomb are made in a one-half inch diameter size, but smaller diameters can be produced in the same press using interchangeable punch and die sets. Complete pellet making instructions are furnished with each press.

Combustion CapsulesNon-volatile samples to be tested in Parr oxygen bombs are weighed and burned in shallow capsules meaning approximately 1” dia. and 7/16” deep. These are available in stainless steel, fused silica and platinum alloyed with a 3-1/2% rhodium. Stainless steel capsules are suitable for all tests except those in which a non-metallic (fused silica) holder is desired or where the superior corrosion resistance of a Pt-Rh cup is required.



Fused silica capsules should be used for samples containing dissolved metals which can ignite a stainless steel capsule and cause serious bomb damage.Stainless steel capsules will soon acquire a dull grey finish after repeated use in an oxygen bomb due to the formation of a hard, protective oxide film. This dull finish not only protects the capsule but it also promotes combustion and makes it easier to burn the last traces of the sample. It is recommended, therefore, that capsules be heated in a muffle furnace at 500°C for 24 hours to develop this protective coating uniformly on all surfaces. This treatment should be performed after a capsule has been polished with an abrasive to remove any ash or other surface deposits. Heating in a muffle is also a good way to destroy any trace of carbon or combustible matter which might remain in the capsule from a previous test. After heating, place the capsules in a clean container and handle them only with forceps when they are removed to be weighed on an analytical balance.

Capsules should be monitored for wear. Do not use the capsule if the wall or base thickness is less than 0.025”.

Foodstuffs and Cellulosic MaterialsFibrous and fluffy materials such as vegetable fibers may have to be packed into the combustion capsule and moistened to slow the burning rate, but foodstuffs and cellulosic samples generally burn with little difficulty. Partial drying may be necessary if the moisture content is too high to obtain ignition. But if the sample is heat sensitive and cannot be dried, a water soluble combustion aid such as ethylene glycol can be added to promote ignition.

Coarse SamplesIn most cases it may be necessary to burn coarse samples without size reduction since grinding or drying may introduce unwanted changes. There is no objection to this if the coarse sample will ignite and burn completely. Whole wheat grains and coarse charcoal chunks are typical of materials which will burn satisfactorily without grinding and with no additives or special procedure.

Corrosive SamplesAlthough the Parr bomb is made of corrosion resistant alloys, repeated use with high sulfur samples or with samples containing over 20 mg of chlorine may corrode the metal surfaces and produce a dull film on the inner walls of the bomb. Materials containing appreciable amounts of caustic; such as dried black liquor from a pulp mill, may also damage the bomb, with the caustic attacking the alloy capsule and causing the metal capsule and the bomb electrodes to ignite and burn. These corrosive attacks on the bomb can be reduced by using smaller samples and by increasing the amount of liquid placed in the bottom of the bomb. If a corrosive film develops on the bomb surfaces it should be removed by proper polishing before it grows to a point where deep pitting occurs.

Liquid SamplesNon-volatile samples are treated in the same manner as solid materials. Oils and other liquids which are not volatile at room temperature can be weighed directly into open combustion capsules. The loop of the fuse

43A6 Combustion Capsule with Adhesive Tape Seal3601 Gelatin Capsules 43AS Combustion Capsules



should be positioned just slightly above the surface of the sample. Some operators place one end of a short piece of fine cotton thread over the fuse loop, with the other end touching the liquid. In any case, the wire itself should not be submerged in the liquid.

Gelatin CapsulesVolatile liquid samples to be burned in an oxygen bomb can be handled conveniently in Parr 3601 Gelatin Capsules. These 0.9 mL capsules consist of two cups which telescope together with a friction fit adequate to retain most liquids. Corrections must be made for the heat of combustion of gelatin (approximately 4600 cal/g) if the capsules are used for calorimetry, and for the sulfur content of the gelatin (approximately 0.35%) if used for sulfur determinations. Blank tests must be run to determine the exact amounts. Gelatin capsules should always be stored in sealed bottles and handled with due regard for their hygroscopic nature.

The blank tests should be repeated at frequent intervals since values determined on a weight basis will change if there are variations in the moisture content of the gelatin.

Tape-Sealed Sample HoldersVolatile samples can be handled in a standard 43AS combustion capsule with a flat top rim, or in a 43A6 platinum capsule with a spun rim by covering the top of the capsule with a disc of adhesive plastic tape. To seal a capsule; stretch a piece of tape across the top and press it firmly against the rim with a flat blade, then trim the excess with a sharp knife. The seal obtained in this manner will be adequate to retain most volatile samples. The tape used for this purpose should be free of chlorine and as low in sulfur as possible. Borden “Mystic Tape” No. M-169-C, or 3M Transparent Tape No. 610 are recommended for this purpose. Equivalent tape can be obtained from Parr under Part No. 517A. The weight of the tape disc must be determined separately and a correction applied for any elements in the tape which might interfere with the determination. This can be done by running a blank test with the tape alone using a sample weighing about 1.0 gram. Tape should always be stored in a sealed container to minimize changes in its moisture content.

Use the following procedure when filling and handling any of these tape-sealed sample holders; Weigh the empty cup or capsule; then cover the top with tape, trim with a knife and press the trimmed edge firmly against the metal rim. Also cut and attach a small flag to the disc; as illustrated at the top of the page. Puncture

the tape at a point below the flag, then reweigh the empty cup with its tape cover. Add the sample with a hypodermic syringe; close the opening with the flag and reweigh the filled cup. Set the cup in the loop electrode and arrange the fuse wire so that it touches the center of the tape disc.Just before closing the bomb, prick the disc with a sharp needle to make a small opening which is needed to prevent collapse of the disc when pressure is applied. Fill the bomb with oxygen to the usual charging pressure, but add oxygen slowly so that the tape will not collapse into the cup. Fire the bomb and complete the test in the usual manner.

Low volatile samples with a high water content, such as urine or blood, can be burned in an open capsule by absorbing the liquid on filter paper pulp or by adding a combustion aid, such as ethylene glycol or by freeze drying the sample.

Heavy OilsOils and other liquids which are not volatile at room temperature can be weighed directly into open combustion capsules. The loop of the fuse should be positioned just slightly above the surface of the sample. Some operators place one end of a short piece of fine cotton thread over the fuse loop, with the other end touching the liquid. In any case, the fuse wire itself should not be submerged in the liquid.

Several precautions must be observed when testing heavy oils because of the intense heat which they develop. If the wall of the metal combustion capsule is thin, or if some of the sample happens to have been spread on the thin rim of the capsule, it is possible that the metal may become heated to the point where it will ignite. This condition is serious because of the excessive heat liberated when metal burns in oxygen. Also, the molten metal oxides may damage the interior of the bomb. In extreme cases the bomb electrodes may also ignite and burn with similar results. For these reasons, be sure that any capsule holding a heavy oil is in good condition and not worn thin from prior usage. Also, bend the straight electrode so that it does not project over the cup where it will receive the full flame from the sample. It is always desirable to tilt the capsule slightly in the loop holder so as to direct the flame away from both electrodes. Some operators prefer to use a 10 to 13 mL platinum crucible for holding heavy oil samples because the added depth in a crucible promotes slower combustion and a milder flame.



Explosives and High Energy FuelsSpecial precautions must be observed when testing materials which release large volumes of gas upon ignition, or which detonate with explosive force. Although most slow-burning gun powders and rocket propellants can be tested in the conventional 1108 bomb, the user must understand that this bomb is not designed to withstand the shock pressures produced by primers and high explosives. It is much safer to test these materials in a Parr 1104 high pressure oxygen bomb.

OPERATING SUGGESTIONS

Poor CombustionThe difference in combustion characteristics of the wide variety of materials which may be burned in an oxygen bomb make it difficult to give specific directions which will assure complete combustions for all samples. However, two fundamental conditions may be stated. First, some part of the sample must be heated to its ignition temperature to start the combustion and, in burning, it must liberate sufficient heat to support its own combustion regardless of the chilling effect of the adjacent metal parts. Second, the combustion must produce sufficient turbulence within the bomb to bring oxygen into the fuel cup for burning the last traces of the sample.

An incomplete combustion in an oxygen bomb is nearly always due to one or more of the following causes:

Excessively rapid admission of gas to the bomb 1. during charging, causing part of the sample to be blown out of the cup.

Loose or powdery condition of the sample which 2. will permit unburned particles to be ejected during a violent combustion.

The use of a sample containing coarse particles 3. which will not burn readily. Coal particles which are too large to pass a 60-mesh screen may not burn completely.

The use of a sample pellet which has been made too 4. hard or too soft. Either condition sometimes causes spalling and the ejection of unburned fragments.

The use of an ignition current too low to ignite the 5. charge, or too high, causing the fuse to break before

combustion is under way.

Insertion of the fuse wire loop below the surface of 6. a loose sample. Best results are obtained by barely touching the surface or by having the wire slightly above the sample.

The use of insufficient oxygen to burn the charge, or 7. conversely, the use of a very high initial gas pressure which may retard the development of sufficient gas turbulence within the bomb.

Insufficient space between the combustion cup and 8. the bottom of the bomb. The bottom of the cup should always be at least one-half inch above the bottom of the bomb, or above the liquid level in the bomb, to prevent thermal quenching.

Excessive moisture or non-combustible material in 9. the sample amounts to approximately 20 percent or more of the charge it may be difficult to obtain complete combustion. This condition can be remedied by adding a small amount of benzoic acid or other combustion aid.

Oxygen Charging PressureOperators sometimes disagree as to the most desirable oxygen charging pressure. As a rule, it is best to use the lowest gas pressure that will give complete combustion. Lower pressures permit higher gas temperatures and greater turbulence, both of which help to secure better combustion. The range of charging pressures for Parr oxygen bombs usually falls between 25 and 35 atmospheres, and it should never exceed 40 atmospheres.

MAINTENANCE AND SAFETY INSTRUCTIONS

Bomb MaintenanceUnder normal usage Parr oxygen bombs will give long service if handled with reasonable care. However, the user must remember that these bombs are continually subjected to high temperatures and pressures which apply heavy stresses to the sealing mechanism. The mechanical condition of the bomb must therefore be watched carefully and any parts that show signs of weakness or deterioration should be replaced before they fail. Otherwise, a serious accident may occur.

Do not fire the bomb if gas bubbles are observed anywhere indicating a possible gas leak. Disassemble



the parts and install new seals immediately. The bomb head parts which require closest attention and most frequent replacement are: the 230A O-ring head gasket, all the 238A sealing rings, the 415A O-ring and the 20VB PCTFE valve seat in the needle valve.

When replacing the 230A head gasket, stretch the new O-ring and let it snap into place to be sure that it moves freely in its groove and is not twisted.

The 20VB valve seat in the needle valve deteriorates with use, not only in the needle area but on the underside of the seat as well. Leakage and a possible serious burn-out can result from a worn or damaged seat if it is not replaced promptly. As a basic rule, the 20VB valve seat and the two 238A O-rings on the valve needle should be replaced after every 500 firings or every six months, whichever occurs first. If the bomb is used for samples containing chlorine, these parts should be replaced after every 250 firings.

To replace the valve seat, unscrew the 397A compression nut; remove the valve stem and the old seat, and disassemble all of the parts. Drop a new 20VB valve seat into the body and push it down into place. Slide a 7VBCM Monel washer, two 238A O-rings and the 378A packing cup onto the A420A valve needle assembly with the needle pointed upward; then adjust the parts on the needle so that the tip of the needle is flush with-or slightly recessed into-the bottom of the packing cup. Insert this assembly into the 396A outlet valve body and press it firmly against the valve seat by tightening the 397A compression nut to 100 inch-pounds of torque.

A Parr 475A Service Clamp offers a convenient means for clamping the bomb head firmly in a vise without damaging the head when replacing any of the bomb head parts.

Keep the 397A compression nut on the valve needle tightened firmly at all times. Frequent tightening is important. This nut, if slightly loose, may allow a leak to develop during the rapid pressure rise upon ignition. This type of leak may not be detectable before firing; but if it develops, the hot gases can ignite the 20VB valve seat and burn through the head.Do not use extreme force when closing the needle valve. A moderate but firm turn on the valve knob should be sufficient to stop all gas flow. Excessive needle pressure will deform and possibly close the gas passage. If this happens, unscrew the valve body and replace the 20VB

valve seat. Accumulated salt deposits may also clog the gas passage, making it difficult to release pressure at the end of a run. To avoid this, clean the passage through the valve needle and deflector nut with a small drill.

The 238A sealing ring in the insulated electrode should be replaced with the same frequency as the 20VB valve seat. Also, keep the 411A terminal nut tight at all times. As the 238A sealing ring ages and hardens it becomes a partial electrical conductor, permitting misfires and producing unwanted heating effects. Periodic replacement will eliminate this potential problem.

The threads on the screw cap should be checked routinely for any burns or other deformity. After long use, the threads on the screw cap may become worn to the point where they will no longer provide a safe closure for the bomb, and the screw cap will have to be replaced. The following procedure can be used to check the extent to which the threads have become worn:

Assemble the bomb with the head in the cylinder and count the number of turns required to bring the screw cap down firmly against the head. Then open the bomb; remove the head and replace the screw cap, but turn it down to only one-half of the turns previously counted. This will usually be about four turns. With the screw cap in this position, use a dial gage to measure the vertical deflection when lifting the screw cap upward. If this measurement exceeds 1/32 inch (0.030”), the screw cap is unsafe and should be discarded. The cylinder can then be returned to the factory for inspection. If the threads on the cylinder are in good condition, a new screw cap can be custom-fitted to the cylinder.

Never under any circumstances use oil on the O-rings which seals the bomb head or on any of the valves or fittings which handle compressed oxygen. This precaution applies to all of the oxygen bombs parts to the oxygen filling connection as well.

Although Parr oxygen bombs are made from alloys which will withstand most corrosive gases, these bombs will not resist chlorine, fluorine or bromine in the presence of moisture. If samples yielding appreciable amounts of these elements are burned in a Parr bomb, the interior surfaces may become etched or corroded. In such cases the bomb should be emptied and washed as quickly as possible after each combustion.

If the interior of the bomb should become etched as mentioned above, the resistance of the metal to further



attack can be improved by restoring the surface to its original highly polished condition. Bombs needing repolishing or other repair work can be returned to the factory. A periodic overhaul and test at the factory will help to keep any Parr oxygen bomb in first-class condition.

Bomb Repairs and Proof TestsThe 20VB valve seat, 230A, 415A, and the four 238A O-rings should be replaced after every 500 firings, or every six months, whichever occurs first. If the bomb is used for samples containing chlorine, these repairs should be made after every 250 firings. Parr oxygen bombs can be returned at any time for repair and testing. A factory test is recommended after every 5000 firings, or after any of the following conditions; (a) fired with an excessive charge, (b) ignition of any internal components, (c) machined by any source other than the factory, (d) damaged by corrosive vapors that might have exceeded 80% of the corrosion allowance, or (e) any changes in the threads on the bomb cylinder and/or screw cap.

When returning a bomb to the factory, ship it to:

Parr Instrument Company Attn: Repair Department211- 53rd StreetMoline, Illinois 61265

A purchase order covering the repair work should be included with the shipment or mailed to the same address as no repairs will be started without specific instructions. Be sure to include a return shipping address and the name and telephone number of the individual to be contacted if questions arise concerning excessive repair costs or other problems. Individual repair parts can be ordered from any Parr dealer or direct from the factory.

1108 PARTS DIAGRAM KEYKey Item Description

1 103A Screw Cap

2 230A O-ring 2-3/8 ID Buna-N

3 394A12394A12CL

Bomb Head, BareBomb Head for Chlorine Service

4 A101A

A101ACL

Bomb Cylinder sold only with 103A Screw Cap as Part No. AA101ABomb Cylinder for Chlorine Service sold only with 103A Screw Cap as Part No. AA101ACL

5 395A2 Inlet Valve Body

6 415A O-ring 7/16 ID Buna-N


8 403A Check Valve

9 411A Terminal Nut

10 143AC Insulator Delrin


12 388A Spacer

13 SC1932SC10 Socket Head Set Screw

14 278A3 Adapter Bushing

15 404A2 Deflector Nut

16 406A Lock Nut

17 5A10 Loop Electrode with Sleeve

18 4A10 Straight Electrode with Sleeve

19 401A Sleeve Insulator

20 96AC Electrode Insulator

21 402A Electrode Core

22 406A Lock Nut

23 407A Valve Knob

24 398A Lock Nut

25 400AA420A

Valve NeedleValve Needle with Knob (Nos. 23, 24, 25)

26 397A Compression Nut

27 396A Outlet Valve Body

28 7VBCM Washer Monel

29 378A Packing Cup

30 20VB Valve Seat Kel-F

Item Complete Assemblies

AA101A Bomb Cylinder with 103A Screw Cap

AA101ACL Bomb Cylinder for Chlorine Service with 103A Screw Cap

A416A3 Bomb Head Assembly

A416A3CL Bomb Head Assembly for Chlorine Service



PARTS FOR THE 1108 OXYGEN BOMB

1

3

10

30

289

19

2

4

5

6

8

7

11

9

29

7

7

27

26

25

24

23

13

12

1520

21

22

18

15

14

16

17



PARTS FOR THE 2901 IGNITION UNIT

200F6

(3) TN1332HL

190F

2005E34E2

SEE NOTE 2

1576E1575E

REF

86F

2014E

(10 cm)

(COMMON)

(3) A59A2

COVERA3299HC

(7 cm)

MOUNT TRANSFORMERW/(4) UP18DM04

2000E

REFTN1632HL

1574E

1557E REF

GROUND SYMBOL

SEE NOTE 1A1580E

CHASSISA3299HC

REF

1157E139E2

174FISO WARNING SYMBOL

REF

(LOAD)

12

12V

12V115V

115V

12

11

8

7

1

2

5

6

4

3

5

4

3

1

2

2

1

6

7

711

11

1210 10

9

8

9

6

8

Item Description

A1673E2 Kit Electric Parts for 2901EB/EE

1203EEE Cord 10A/220V Cont Europe Plug

1202EEE Cord 13A/220V BS Plug

2000E Transformer, 120/240 VAC 24V

XB0010 1/8ID Shrink Tubing Black

34E2 Cord w/ 115VAC Plug 18-3SJT

A3299HC Box Assembly, Ignition Unit 115V

A3299HC2 Box Assembly, Ignition Unit 230V

2005E Strain Relief Pigtail Black

2005E2 Strain Relief Pigtail Black, for 230V

139E2 Fuse Fast/Act 1.5 Amp 3AG 250V

139E6 Fuse Fast/Act 1 Amp 250V

1157E Fuse Holder, 3AG x 1/4 Tab

SA1332RP04 6-32 x 1/4 RHMS Phillips 18-8

Warning:

For continued protection against possible hazard, replace fuses with same type and rating of fuse.



PARTS FOR THE 1825 OXYGEN FILLING CONNECTION

Item Description

4VB3 Packing gasket

6VBBB Packing cover, brass

8VB2 Packing nut

9VB1 Union nut, brass, CGA540

20VB Valve seat, PCTFE

21VBBB Lantern ring, brass

53A Oxygen gage, 3-1/2”, 0-60 atm

112VB4AK Valve needle

124VB Union nipple, brass, CGA540

A140VB Toggle relief valve

A150VB Valve knob

188A2 Filling connection body, bare

243VB Tube connector, male

438VB Elbow connector, 45°, male

A476A3 Slip connector with O-rings

394HCJE O-ring for A476A3 slip connector (2 required)

HX0012TB024 Pressure tubing, 1/8” OD, Nylon, 5-ft

211 53rd StreetMoline, Illinois 61265 USAPhone: 1-309-762-7716 or 1-800-872-7720Fax: 1-309-762-9453E-mail: [email protected]://www.parrinst.com

Parr Instrument Company

Revision 05/21/10

Documents

205M Parr 1108 Oxygen Bomb Inst